1. Field of the Invention
This invention relates to liquid cooling systems of the type normally used in connection with internal combustion engines.
More particularly, the present invention relates to closure and valving devices for the filler neck of the radiator of a pressurized liquid cooling system.
In a further and more specific aspect, the instant invention concerns an improved closure and valving apparatus especially having means for preserving the integrity of the sealing engagement with the filler neck.
2. Prior Art
The primary function of an internal combustion engine is the conversion of the potential energy contained within fuel, usually gasoline or diesel oil, into a form which can be harnessed to perform useful work As a result of combustion of the fuel within the engine, the potential energy is released as heat. Approximately one-third of the heat energy is converted into power. Another third is discharged through the exhaust system. The final third is absorbed by the engine.
Within limits, the heat which serves to elevate the temperature of the engine is beneficial. It is a well established fact that what is commonly referred to as a "warm engine" operates nearer optimum efficiency than a cold engine. Continued heat absorption, above desirable limits, is extremely deleterious, ultimately resulting in the destruction of the engine.
To control temperatures within safe limits by removing excess heat, internal combustion engines are commonly provided with a liquid cooling system. In the conventional cooling system, heat is absorbed from the engine and transferred for dissipation to the atmosphere. Within the closed heat-transfer loop of the system, liquid functions as the heat transfer medium. Hence, the engine is referred to as being "liquid cooled".
Conventionally, the liquid cooling system for a typical internal combustion engine includes a water jacket, generally a plurality of inner connected passages or a single circuitous passage within the engine. The water jacket circumferentially embraces each of the one or several combustion chambers in which heat is generated as a result of the combustion of fuel.
Remote from the engine, usually in front thereof in an orthodox installation, is a radiator essentially including a core positioned between a pair of tanks. The core, being a heat exchanger, comprises a plurality of relatively small tubes surrounded by fins and air passages. At one end, the tubes communicate with an inlet tank. An outlet tank is located at the other end of the tubes. A conduit, colloquially referred to a radiator hose, extends between the outlet of the water jacket and the inlet tank. A similar conduit communicates between the outlet tank and the inlet of the water jacket.
A tubular member, referred to as a filler neck and extending from the inlet tank, provides means for introducing liquid into the system. The free end of the filler neck, in accordance with conventional manufacture, terminates with an outwardly directed annular ledge concluding with a depending circumferential skirt. An apparatus, commonly dubbed a radiator cap, is detachably securable to the circumferential skirt. Traditionally, an annular gasket carried by the cap seals against the annular ledge when the cap is fully engaged with the filler neck.
Within the system, heat is transferred by circulating liquid known as coolant. Excess heat generated by the engine is absorbed by the coolant within the water jacket. The circulating coolant carries the heat to the radiator, through the inlet tank and into the tubes of the core. In response to air passing through the core and the tubes, the heat is dissipated into the ambient atmosphere. The coolant, now being of lower temperature, flows through the outlet tank and is returned to the water jacket thereby displacing heated coolant.
Initially, radiators were gargantuan. The tubes extended vertically. The inlet tank resided atop the core, while the outlet tank was located underneath. In order to maintain a reserve supply of coolant and allow for expansion of the liquid, the inlet tank was of substantial capacity.
As a result of the functions performed, inlet tanks became known by various terms. Among these are "expansion tank", "water tank", "radiator tank", "top tank", "surge tank", and "reservoir". Although no longer appropriate in view of modern design, the archaic terminology persists. The designation "header tank", however, is apropos for either inlet or outlet tank.
Liquid cooling systems of early prior art design depended upon natural circulation, or thermosiphon, as a result of specific gravity differences of water within the system. Water, heated in the water jacket surrounding the combustion chambers, rises within the loop system to the inlet tank of the radiator. Cool water is drawn into the water jacket from the outlet tank of the radiator. Water is also displaced downwardly through the radiator for cooling. Depending upon constantly changing differences in specific gravity the cycle is continuous. The speed of circulation is proportional to the heat output of the engine.
Cooling systems relying upon thermosiphon have proven to be fairly adequate with engines of low-output, low-compression design. With the advent of more modern engines of greater horsepower and increased heat generation, thermosiphon was no longer effective. Lower hood profiles of motor vehicles also demanded more compact radiator design. Accordingly, forced circulation of air and coolant became a standard practice.
A pump was placed into the cooling system. Conventionally, the pump was secured to the engine at the inlet to the water jacket and received the hose extending from the outlet tank of the radiator. A fan was secured to the shaft of the pump immediately behind the radiator.
Other innovations of approximately the same era and made possible by the occurrence of forced circulation, further contributed to the historical development of the cooling system. Two notable improvements were pressurization of the system and the introduction of alternate cooling liquids. Cooling efficiency was increased, higher operating temperatures were possible, and corrosion was reduced.
To facilitate pressurization, there was introduced a radiator cap having a lid or cover member which extended over the free end of the filler neck. Generally a sheet metal stamping, the cover member included a pair of diametrically opposed tabs which engaged the downturned skirt at the free end of the filler neck. To prevent rotation of the cap, a spring friction diaphragm bore against the end of the filler neck. A compression spring, bearing at the upper end against the cover or the diaphragm, urged a gasket into seated engagement against a seat formed by an inwardly directed shoulder, usually including a raised annular bead, at the lower end of the filler neck. The several components were assembled by a rivet extending through the cover member. For purposes of relieving excess pressure within the system, the spring and gasket were known as the relief valve. Steam and hot water were expelled under the spring fiction diaphragm or through an overflow vent, usually in the form of a radially projecting nipple, residing intermediate the ends of the filler neck. Also included was a valve to relieve any vacuum created within the system as a result of cooling.
To augment the benefits of pressurization and further increase engine efficiency, an alternate coolant was introduced. The coolant was a mixture of antifreeze and water. In addition to providing cold weather protection, the mixture increased the allowable operating temperature before boiling. Further, the mixture reduced system corrosion.
It is now well known that in order to increase the operating temperature substantially above the boiling point of water, a highly desirable condition that will be readily recognized by those skilled in the art, a judicious selection of radiator cap design and coolant mixture is recommended. A common coolant mixture is one-half water and one-half antifreeze, such as ethylene glycol. This mixture increases the boiling point to 226 degrees F., 14 degrees F. above that of water.
The boiling point of a liquid under pressure is raised approximately 3 degrees F. for each one pound per square inch (1 psi) of pressure. Since the coolant system is pressurized, the boiling point is accordingly increased. A system operating under 15 psi with a mixture of equal parts water and antifreeze will, therefore, boil at approximately 271 degrees F.
It is apparent, therefore, that a cooling system utilizing a properly proportioned coolant mixture will operate with a maximum positive pressure as determined by the radiator cap. When the predetermined value of the spring is reached, the relief valve opens allowing discharge of the liquid coolant through the vent of the filler neck. Subsequently, as the temperature and pressure subside, as when the engine cools after being shut down, the relief valve closes and the vacuum valve opens to relieve the negative pressure or partial vacuum created by a contraction of the coolant.
Historically, as a result of repeated cycles of heating and cooling, substantial quantities of the liquid coolant containing the expensive antifreeze are lost, having been discharged through the vent to fall upon the ground. The mixture, precious to proper cooling, was supplanted by ambient air, a less efficient cooling medium. Accordingly, it was convention of the era for motorists to carry a supply of a make-up liquid, usually plain water.
During relatively recent times, the art sought to provide a remedy for the loss of coolant. Concurrently, the art addressed a problem previously ignored, but nevertheless known, from almost the beginnings of liquid cooling systems for internal combustion engines. Air, entrained within the liquid coolant, in addition to reducing efficiency, produced various deleterious effects including cavitation of the water pump, corrosion of the water jacket, and premature oxidiation of radiator hoses. It was also recognized that periodic removal of the radiator cap, necessitated by frequent need to check the coolant level, added additional air to the system. Further, removal of the cap presented potential personal safety hazards due to the presence of the hot or steamy coolant mixture.
The proposed remedy was in the form of method and apparatus for purging air from the cooling system. Included was an accumulator tank positioned within the engine compartment remote from the radiator. A conduit communicated between the normal vent or overflow of the filler neck and the lower part of the accumulator tank. An air vent was formed in the top of the accumulator tank.
The apparatus made use of the phenomenon that free air, if any, within the system will rise to the top of the inlet tank. Coolant, rising as a result of thermal expansion, will displace the air which will be forced out through the vent and the conduit into the accumulator tank. In reality, most air will be purged in a foamy or vaporous combination with coolant. Depending upon the heat build-up, a quantity of coolant will follow the air and the vaporous combination into the accumulator tank.
Once in the tank, the overflowed vapor or foam condenses. The air effervesces upwardly and escapes through the vent into the atmosphere. The deaerated coolant settles to the bottom of the accumulator tank. As the system cools, only deaerated coolant will be siphoned back through the vent valve.
The foregoing system, generally referred to as "overflow recovery", was favorably accepted and achieved substantial commercial success. The success was particularly pronounced within the motor vehicle art, especially passenger cars and light trucks. The functioning of the apparatus, however, as observed over a period of extended use, subverted the method. The primary contributor to the inferior result was the radiator cap.
Various types of caps have been used and currently are being used in connection with the system. A commonly employed cap is an adaption of conventional earlier design. Carried forward is the original stamped metal lid or cover member. An upright cylindrical element, also a metal stamping, having an upper end wall and an outwardly directed annular lip at the lower end, and frequently referred to as the "link" is axially secured to the underside of the cover member. A generally bell-shaped element, again a sheet metal stamping and generally called the "housing", is telescopingly engaged with the link. A pressure gasket and a vent valve are carried by the housing. A compression spring, encircling the link, biases the housing in a direction away from the cover member to urge the pressure seal into normal sealing engagement with the seat formed at the fixed end of the filler neck.
Variations of the primary configurations are known. For example, the basic design includes an atmospheric seal which sealingly engages the annular seat formed at the free end of the filler neck. In accordance with one scheme, the seal is carried by the cover member. An annular gasket is secured to the underside of the spring diaphragm in an alternate embodiment.
Differing means of attaching the link to the cover member are also practiced. In strict compliance with the prior art, the rivet remains as the attachment element. In a modified version, the upper end wall of the cylindrical link is bonded, such as by spot welding, to the underside of the lid.
An hermetic seal between the lid and the filler neck, at a location above the overflow vent of the filler neck, is mandatory for proper functioning of the system. It is now well known that to alleviate negative pressure or vacuum, the system will preferentially draw air through even the slightest of openings rather than siphon liquid from the accumulator tank. Accordingly, it is recommended that make-up coolant, if necessary, be added through the accumulator tank and that the radiator cap be removed only for occasional inspection. Owners, operators, and service station attendants not yet ready to rely upon the coolant level within the accumulator tank, frequently remove the radiator cap.
Radiator caps of the type having an atmospheric seal rotatable with the cover member are soon rendered worthless as a result of the seal being abraded against the filler neck. A similar phenomenon accelerates destruction of the pressure seal which is prohibited from rotation as a result of spring friction against the cover member and the housing. Inferior pressure spring configuration also contributes to deterioration of the pressure seal.
Experience has also shown that gasket-type atmospheric seals carried by the spring diaphragm are highly ineffective. Excessively pressurized coolant, having opened the pressure valve, is capable of unseating the gasket from the end of the filler neck and escaping to be lost from the system. The immediate type of seal also permits the hazardous, forceful emission of superheated steamy coolant when the cap is rotated to the vent or safe position.
Other inadequacies are inherent in radiator caps of riveted type construction. Initially, it is virtually impossible to set the rivet in the manner which will satisfactorily seal the opening through the cover member or the lid. Even if an acceptable mechanical bond is achieved during manufacture, the joint quickly loosens under the stress of use. In recognition thereof, certain manufacturers supply an auxiliary seal, usually in the form of an attachment to the exterior of the lid, over the rivet. Such auxiliary seals eventually deteriorate under conditions of actual use.
As a departure from the historical standard, the more modern art has devised radiator caps of non-metallic material, such as molded resinous plastic. One configuration is reminiscent of the more conventional metallic design. The former housing element is replaced by a disc-like membre, more appropriately called a pressure pad, having an upstanding projection. A cylindrical element, the approximate equivalent of the metallic link integrally depending from the cover member, telescopingly receives the projection extending from the pressure pad. The bore of the cylindrical element extends through the cover member and is closed by an external plug. The device utilizes a spring diaphragm fabricated of resinous material. At the lower end, the pressure spring encircling the cylindrical element bears against the pressure pad. The spring diaphragm is pressed against the cover member by the upper end of the pressure spring.
The newly developed apparatus adequately eliminated certain shortcomings of the more tradionally patterned devices. The resinous material is less susceptible to corrosion from contact with steam or antifreeze compounds. Being an inherently poor thermal conductor, the cover member does not represent a potential source of burns to the hand of an attendant. Also, the use of mechanical fastening means, such as rivets or spot welding, is eliminated.
New concerns, however, arose. In general, the components are more intricate. Injection molds, for creating the several resinous components, are expensive. In order to provide sufficient rigidity and withstand engine operating temperatures, the plastic is reinforced by glass filling. Glass, being a high friction material, lends an undesirable characteristic to certain of the components.
Other undesirable features remained. Exemplary, the opening through the cover member will still present the potential for system nullifying leakage. The previously described problems associated with the spring diaphragm are still in attendance.
A later developed radiator cap, also fabricated of resinous material, is endowed with various art enhancing features. The link, now an inverted cup-like component, carried by the cover member, supports the pressure pad and receives the pressure from the upper end of the spring. Thus, rotation retarding friction generated by the pressure spring is successfully eliminated. The device is fabricated of a relatively few, simple interlocking components. Dismissed was the previously present assembly opening through the cover member, the current design being monolithic.
Complementing the impervious cover member is a relocated atmospheric seal. Carried in a gland, or groove, formed into the cup-like link, or a cylindrical projection depending from the cover member, or partially in each, the atmospheric seal engages the inner cylindrical side wall of the filler neck. Accordingly, the seal remains intact in both the vent and the locked positions.
This structure, however, has not presented a perfect solution. Use of a molded cover member of resinous material is mandatory. The union between the link and the cover member is relatively intricate. Due to the extended engagement between the atmospheric seal and the filler neck, separation of the cover member from the link has been experienced.
It is apparent at this time, that no single specific configuration of a radiator cap has received universal acceptance. Those skilled in the art are dispersed, manufacturing and marketing a diverse array of radiator caps. A share of the diversity finds bases in functional objections. Other dispersion results from preference, partially subjectively contrived, of the various manufacturers.
For example, while it is generally conceded that the placement of the atmospheric seal within the filler neck is preferential, inherent design characteristics has precluded the concurrent use of a spring diaphragm or a gasket which will seat against the free end of the filler neck, considered by some to be desirable features. Also, manufacturers have been maneuvered into a position of selecting either a metallic radiator cap with the attendent features or a plastic unit with alternate attributes. In general, the art has heretofore been denied the advantageous qualities of each.
The cooling system has become highly critical as a result of further advances of automotive technology. Constantly lowering hood silhouettes, requiring decreased radiator size, and increased output per displacement ratios of engines, requiring greater cooling capacity, has imposed severe burdens upon the cooling systems. As a partial solution, the art has developed the "cross-flow" radiator in which the inlet and outlet tanks are disposed upright along either side of a core having horizontal tubes. Nevertheless, it remains that coolant system failure is the primary mechanical misfunction resulting in road break downs of motor vehicles. It is imperative, therefore, that each component of the cooling system of an internal combustion engine be maximally efficient.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide an improved closure and valving apparatus especially adapted for use with the filler neck of the radiator of a pressurized liquid cooling system.
Another object of the invention is the provision of a closure and valving apparatus (radiator cap) having improved means for sealing engagement with a conventional filler neck.
And another object of the invention is to provide a radiator cap having new and novel means for preserving the integrity of the sealing engagement.
Still another object of the instant invention is the provision of a radiator cap having a sealing and valving assembly which is freely rotatably carried by a lid or attachment member.
Yet another object of the invention is to provide means whereby a predetermined sealing and valving assembly may be used with alternate attachment members of various design.
And still another object of the immediate invention is the provision of a radiator cap having accommodations for plural atmospheric seals.
A further object of this invention is to provide improved seal supporting means.
And a further object of the invention is the provision of a device capable of withstanding repeated engagement and disengagement with the filler neck.
Still a further object of this invention is to provide a closure and valving apparatus of simplified design.
And still a further object of the invention is the provision of closure and valving apparatus, according to the above, which is relatively inexpensive to manufacture.
Yet still a further object of the instant invention is to provide means for extending the life of the pressure seal.